This is an overview of some of the main family members.
The Rivett Family are connected to the Forsdyke Family via the marriage of Ann Rivett and Thomas Forsdike on 15th November 1840 in Falkenham, Suffolk. Although I have access to Parish Registers for Falkenham, I have been unable to find much information on Ann Rivett's ancestors. I believe her Grand-father was Benjamin Rivett born circa 1762 in Falkenham, but I have no idea who her Grand-mother was nor when her Grand-parents married. I do know however that Benjamin Rivett died in 1848 from the Civil Registrations for Woodbridge, Suffolk.
Only one son has been found for Benjamin, namely James Rivett born 1791 in Falkenham, who married Ann (maiden name unknown) possibly circa 1809. They had 5 children: William 1810, James 1811, Mary 1812, Ann 1815 and Sarah 1822. There is a long gap between Ann and Sarah so there may well be some more children for which records have been lost.
Ann was born on 5th December 1815 in Falkenham and married Thomas Forsdike on 15th November 1840 also in Falkenham.
I also have transcripts of the Parish Registers for Kirton, Suffolk which is closely situated to Falkenham. These registers record a lot of Rivetts and it is reasonable to assume that the Falkenham and Kirton Rivetts are related from earlier generations but I have been unable to go back far enough to find the connection.